It was a test with an outside company. There were charging lockers in the Space Mountain gift shop too. They were removed after about 6 months or so at most.
I was always expecting Disney to bring them back in some form using Magic Bands as it was said to be just a test at the time, but they never did. The problem with these is that there's such a limited amount of slots and they were always full.
It was explained to me once I started working in MK that they were never brought back because guests would simply leave their phone there all day, hogging up slots for people who actually needed to charge their phone.
Whether that is true or not, i'm not sure.